The ability of users to access programs and share data over local area networks (referred to as “LANs”) has become a necessity for most working environments. To improve efficiency and ease of use, certain enhancements may be added to a LAN such as remote wireless access. By providing remote wireless access, a wireless LAN (WLAN) is formed.
As described in U.S. Pat. No. 5,987,062 issued to Netwave Technologies, Inc., now owned by Nortel Networks Limited of Ontario, Canada, one type of WLAN employs dedicated stations, which are referred to as access points (APs). Therein, each AP is a relay station that includes a radio frequency (RF) transceiver that receives radio data packets from a mobile unit (MU) such as a notebook-type computer with a suitable adapter card as described in U.S. Pat. No. 5,987,062. Thereafter, the AP transmits the data packets to the fixed backbone network. Of course, the AP may receive data from the fixed backbone network and transmit it to one or more mobile units.
Before data transmission can occur between the fixed backbone network and an MU by way of an AP, the AP must first authenticate the MU. The authentication is accomplished by the MU transmitting a request for authentication message to the AP, and the AP sending back a successful authentication message back to the MU. Once the MU has been authenticated, the MU has to associate itself with the AP. The association is accomplished by the MU transmitting a request for association message to the AP, and the AP sending back in a successful association message. The authentication and association transmissions are specified in the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. Once the MU has been properly authenticated and associated with the AP, then data transmission between the MU and the fixed backbone network can occur.
A problem with the current wireless network system deals with systems that have more than one sub-network and roaming of MUs can occur between two or more sub-networks. Specifically, when an MU becomes authenticated and associated with a particular AP, the sub-network to which the AP is attached dynamically assigns a network protocol address to the MU. The assigned network protocol address is only valid for that sub-network. It is not valid for other sub-network(s) of the wireless network system. Thus, if the MU were now to roam to a new AP associated with another sub-network, the previously-assigned network protocol address for the MU is no longer valid for the new sub-network. In this situation, the MU can transmit data to the new sub-network, but data transmitted back to the MU ends up being routed to the original sub-network, which the MU is no longer associated with. Thus, the MU would not receive the data addressed to it.
A known prior art technique that deals with this specific problem is known in the art as “mobile IP.” A wireless network system that uses “mobile IP” includes a sub-network that has specialized devices that will forward data to an MU when it roams to a new sub-network. However, a “mobile IP” system is typically very complex, requires a very comprehensive set-up, and is not widely available.
Thus, there is a need for a system and method in a wireless network system for an MU (deemed herein as a wireless unit (WU) since an MU need not be mobile) to automatically obtain a new and valid network Protocol address when the wireless unit (WU) roams from an AP associated with a first sub-network to an AP associated with a second sub-network. Such a system and method is provided herein in accordance with the invention.